The present invention relates to the structure for fixing a check valve.
JP-A 10-250544 discloses a brake control system which can generate a braking force even when a driver provides no brake-pedal operation. With this system, a pump is driven to produce the hydraulic pressure in response to the running conditions of the vehicle, which is supplied to a wheel cylinder, thereby actively generating a braking force even when a driver provides no brake-pedal operation. Such control for actively generating a braking force is referred hereafter to as active brake control.
The brake control system comprises a check valve for permitting brake fluid to flow in one direction only. In the above reference, a check valve is arranged in a passage connecting a reservoir, a pump, and a master cylinder to permit brake fluid to flow from the reservoir to the pump and the master cylinder, and prevent it from flowing from the master cylinder and the pump to the reservoir.
Typically, the check valve comprises a valve-seat member arranged in a passage of a housing or base body and including a valve seat, a return spring for biasing a valve element seated on the valve seat in the closed direction to provide a predetermined checking force, and a socket member mounted to the valve-seat member and for supporting the return spring and restricting a radial displacement of the valve element. The structure for fixing the check valve to the housing is obtained by fixing the socket member to the valve-seat member by fitting, inserting the valve-seat member in the passage of the housing, and crimping an open end of the passage for fixing.
However, as is designed such that the socket member is fixed to the valve-seat member by fitting, and the valve-seat member is fixed to the base body by crimping, the above check-valve fixing structure raises the following problem to be solved:
1) Fitting of the socket member to the valve-seat member needs an overlap width for fitting. Moreover, fixing of the valve-seat member to the base body, which is carried out by crimping or the like, needs also an overlap width for crimping. Since the axially extending overlap widths for fitting and crimping should be arranged between the base body and the valve-seat member and the valve-seat member and the socket member, respectively, increasing the overall length or size of the check valve.
2) Assembling of the check valve needs two kinds of work, i.e. work for engaging the socket member with the valve-seat member and work for crimping the valve-seat member to the base body, having rather large number of assembling operations, leading to a time expense and a cost increase.
3) The components of the check valve undergo a brake-fluid pressure. Thus, with the above structure of engaging the socket member with the valve-seat member, if the brake-fluid pressure causes the socket member to be displaced in the disengaging direction with respect to the valve-seat member, the seating position of the return spring is displaced coincidentally, leading to reduced biasing force to the valve element. Then, a checking force of the check valve can vary, failing to provide a desired operation.
It is, therefore, an object of the present invention to provide the structure for fixing a check valve, which allows not only a reduction in size, number of assembling operations, and manufacturing cost for the check valve, but also a stabilization of a checking function thereof.
The present invention provides generally a structure for fixing a check valve with a valve-seat member having a through hole and a valve seat arranged at an opening end of the through hole and having a valve element seated thereon, a socket member mounted to the valve-seat member to cover the valve element, the socket member restricting an amount of displacement of the valve element within a predetermined value, and a return spring arranged on the socket member to biasing the valve element in a seating direction, wherein the structure comprises: a base body, the base body being formed with a passage in which the check valve is inserted; a receiver formed in the passage; and a flange formed with the socket member, the flange being engaged with the receiver when the check valve is inserted in the passage, wherein with the flange being placed on the valve-seat member and abutting on the receiver, the base body is crimped at an opening end of the passage to fix the socket member and the valve-seat member to the base body.